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General Kenneth Nichols and the Manhattan Project
Nichols
The Oak Ridger has published the latest in a series of articles about General Kenneth D. Nichols, the Manhattan Project, and the 1954 Atomic Energy Act. The series has been produced by Nichols’ grandniece Barbara Rogers Scollin and Oak Ridge (Tenn.) city historian David Ray Smith. Gen. Nichols (1907–2000) was the district engineer for the Manhattan Engineer District during the Manhattan Project.
As Smith and Scollin explain, Nichols “had supervision of the research and development connected with, and the design, construction, and operation of, all plants required to produce plutonium-239 and uranium-235, including the construction of the towns of Oak Ridge, Tennessee, and Richland, Washington. The responsibility of his position was massive as he oversaw a workforce of both military and civilian personnel of approximately 125,000; his Oak Ridge office became the center of the wartime atomic energy’s activities.”
F. C. Schoenig, Jr., F. A. White, F. Feiner
Nuclear Science and Engineering | Volume 37 | Number 1 | July 1969 | Pages 66-84
Technical Paper | doi.org/10.13182/NSE69-A20899
Articles are hosted by Taylor and Francis Online.
The temperature dependence of epithermal neutron capture and fission in enriched uranium-dioxide rods has been measured in a 1/E epithermal spectrum. Experiments performed to 1525°C in the reflector of the Thermal Test Reactor (TTR) have studied the Doppler effect on 235UO2 fission, and experiments to 1278°C in the core of the Union Carbide Research Reactor have investigated the Doppler effect on 235UO2 capture and fission. The samples were cylindrical pellets, 0.341 in. in diameter, mounted between similar pellets to simulate a rod. This UO2 rod was irradiated at various temperatures in a cadmium-covered furnace which was water-cooled so that the temperature of the furnace exterior was that of its environment. Three dilute gold-in-aluminum alloy wires were placed symmetrically about the furnace exterior for neutron flux normalization. The relative numbers of neutron-induced captures and fissions in the 235UO2 samples were determined separately using mass spectrometry and gamma-ray spectrometric techniques. The number of neutron-capture events was determined by mass-spectrometrically measuring the ratio of 236U to 235U in irradiated and unirradiated samples. The number of neutron-induced fission events was determined by the gamma-ray counting of an appropriate fission product. The measurement of the Doppler effect on fission in 235UO2 over four temperature intervals to 1525°C in two irradiation facilities determined that the Doppler effect increased the effective fission integral of this rod by 2.8 ± 1.0% over the temperature interval 24 to 1525°C. A Doppler fission effect of 4% over this temperature was calculated. The Doppler effect on 235UO2 capture has been measured to be 15.5 ± 1.8% over the temperature range 241 to 1278°C, which is ∼2.7 times greater than the calculated effect. These results are consistent with previous 235U Doppler reactivity experiments in which the calculated Doppler reactivity effect was two to three times less negative than the measured value. The effective fission and capture integrals for the enriched UO2 samples have been measured to be 151 ± 18 and 67 ± 8 b, respectively, at 24°C, and are in agreement with the calculated values of 144 and 60 b. Included in this paper is a review of previous measurements of 235U Doppler effects, reported in a consistent set of units. This summary is important in understanding the relative contribution of capture and fission on the 235U Doppler effect and the effect of the neutron energy spectrum on these contributions.
